This invention relates generally to filtration systems and methods and, more particularly, to a filter assembly intended to remove impurities from a liquid, such as a lubricant, and, more specifically still, to a hybrid spin-on oil filter assembly for use with an internal combustion engine, where the hybrid spin-on oil filter assembly is form and fit compatible with a conventional oil filter assembly, but which provides a dual-stage filtering action that includes a conventional oil filter in combination or in parallel with a bypass oil filter capable of filtering and retaining particles of size one micron or greater.
Conventional internal combustion engines used in automobiles and similar vehicles include a spin-on oil filter assembly for cleaning the motor oil. However, due to the fact that the conventional oil filter assembly only effectively removes particles of size 10 microns and larger, after some period of time smaller particles build up in the engine oil and require that the engine oil be replaced. Typical engine oil, and oil filter, replacement schedules are every 3,000 miles or three months, whichever occurs first.
It is known in certain types of vehicles, such as large trucks, to use an auxiliary bypass filter for additional filtering. A typical bypass filter retrofits to the truck engine where it diverts oil through a finer auxiliary filter element at a slower flow rate than the normal oil filter (e.g. 2.5 gallons per minute or less versus about 20 to 40 gallons per minute). Passing the engine oil through the auxiliary filter element aids in filtering out particles smaller than about 40 microns in size, thereby improving engine oil life as well as the life of the engine. Reference in this regard can be had to, for example, U.S. Pat. No. 5,552,065, Meddock et al.
However, this type of filtering arrangement is not typically suitable for use with automobiles and similar types of vehicles. A first issue relates to the difficulty in retrofitting a bypass oil filter assembly to the engine. In many cases there may simply not be room to mount the bypass oil filter assembly. A second issue relates to cost, as the use of the bypass oil filter assembly is inherently more costly than the use of only the conventional type of oil filter assembly.
As can be appreciated, there is a significant body of prior art that has been built up over the decades relating to oil filters and related techniques for internal combustion engines. Representative of this prior art are the following U.S. patents.
In U.S. Pat. No. 3,986,960, Wire et al., describe a fluid filter containing a tubular canister having a contaminated fluid inlet and a filtered fluid outlet. The filter includes a solid tube forming a vertical central conduit within the canister and a plurality of axially space-apart containers mounted serially along the tube. Filtering material is located in the canisters. Ports in the tube communicate with chambers formed between the filter element and the bottom of the container. A seal is effected between the outlet of the canister and the tube, while fluid communication is provided between the inlet and the open tops of the containers such that fluid flow occurring between the inlet and the outlet takes place through the filter elements.
In U.S. Pat. No. 4,048,071, Yamada et al. describe a liquid filtering device where the peripheral surface of a coil of a filter web wound about a hollow shaft is covered by a liquid-impervious flexible coating, and the outer periphery of a first end of the coil is secured to a supporting disc so that when liquid to be filtered is caused to pass through the coil in the axial direction of the coil, the convolutions of the coil near a second end expand radially outwardly to trap contaminants in the spiral gap. Purified liquid collected at the first end of the coil is discharged through the hollow shaft. The filter unit is constructed such that a number of unites can be connected in series.
In U.S. Pat. No. 4,738,776 Brown describes a lubricant filter assembly for an internal combustion engine that includes a head member removably mounted on a base member. The head member includes a sleeve-like housing open at one end and having first and second filter units fixedly mounted therein. The outer peripheries of the filter units coact with the interior surface of the housing to form a common inlet passage. One of the filter units is provided with an interior first outlet passage which communicates with a first passage formation formed in the base member. The first passage formation communicates with a first lubricating circuit of the engine. The second filter unit is provided with an interior second outlet passage which communicates with a second passage formation formed in the base member. The second passage formation communicates with a second lubricating circuit of the engine. Seal sections are carried by the head member. One seal section effects a sealing engagement between the base member and a portion of the housing defining the open end. A second seal section is disposed within the housing and prevents direct communication between the inlet passage and the first outlet passage. A third seal section is disposed within the housing and prevents communication between the first and second outlet passages. The sealing engagement effected by the third seal section is enhanced upon the flow pressure within the interior first outlet passage being increased.
In U.S. Pat. No. 5,178,753 Trabold describes an oil filter for internal combustion engines that is used in a secondary oil circuit in addition to a conventional oil filter. The oil filter includes a filter housing in which a filter element consists of a roll of absorbent paper that is wound about a rod. The oil filter is configured as a set of elements that comprises body sections and caps, and a rod with the rolled filter element. The volume of the oil filter can be matched to a particular application by connecting a plurality of body sections with an appropriate number of rods.
In U.S. Pat. No. 5,556,543 Trabold describes an oil filter for internal combustion engines. The oil filter includes a filter housing and a filter packing made of a porous deformable material, e.g., a roll of absorbent paper. To prevent the filter packing from being deformed and thereby preventing a smooth flow through the filter packing, stabilizing elements, e.g., stabilizing bars, are provided for fixing the form and position of the filter packing within the filter housing.
A long-felt and unfulfilled need exists to provide an oil filter assembly for an internal combustion engine that provides, within a conventionally-sized oil filter container, a conventional oil filter and a bypass oil filter capable of entrapping and thus removing smaller particles from the oil than the conventional oil filter.
Prior to this invention, this need was not adequately fulfilled by the prior art filter assemblies and methods that are known to the inventor.
It is a first object and advantage of this invention to provide an improved oil filter assembly.
It is a further object and advantage of this invention to provide an improved oil filter assembly that contains a first oil filter as well as a bypass oil filter, capable of filtering out smaller particulates from the oil flow than the first oil filter, where the oil filter assembly is form and fit compatible with a conventional oil filter assembly.
The foregoing and other problems are overcome and the foregoing objects and advantages are realized by apparatus and methods in accordance with embodiments of this invention.
An oil filter assembly for use with an internal combustion engine provides, within a conventionally-sized oil filter container, a first or primary oil filter and a bypass oil filter that is capable of entrapping and thus removing smaller particles from the oil (e.g., one micron or greater) than the primary oil filter. The resulting primary oil filter and bypass oil filter assembly, also referred to herein as a hybrid oil filter assembly, is preferably form and fit compatible with a conventional oil filter assembly. That is, the hybrid oil filter assembly can be used to replace a conventional oil filter assembly without making or requiring any modifications to the engine or the filter housing. Furthermore, the hybrid oil filter assembly in accordance with the teachings of this invention is designed to be cost-competitive with the conventional oil filter assembly, especially when one considers the extended oil, oil filter and engine lifetimes that are achieved. The hybrid oil filter assembly is also amenable to being mass produced, and does not require the use of any non-standard materials or components during its manufacture.
In accordance with the teachings of this invention an oil filter assembly includes a housing and a first (e.g., a primary or conventional) oil filter element disposed in proximity to a bottom portion of the housing. The first oil filter element contains an open inner volume, also referred to herein as a void. A second oil filter element having a generally circular cylindrical shape is disposed circumferentially about a length of the first oil filter element. The second oil filter element may be made of rolled cellulose such as paper, and filters particles of a smaller size than the first oil filter element. In further embodiments of this invention the second oil filter element can be comprised of other filtering media, such as glass wool, plastic, cotton, as well as combinations of two or more of these as well as other filtering media suitable for entrapping particles from the oil that are smaller than the particles entrapped by the primary oil filter element.
A first oil inlet is disposed at the bottom portion of the housing for providing oil to be filtered to side surfaces of the first oil filter element, wherein filtered oil flows through a thickness of the first oil filter element to the centrally located open inner volume, and from the centrally located open inner volume through an outlet of the filter housing.
A second oil inlet is also disposed at the bottom portion of the housing and surrounds the first oil inlet. The second oil inlet provides oil to be filtered to a bottom surface of the second oil filter element.
A fluid communication path is provided from a top surface of the second oil filter element into the open inner volume of the first oil filter element such that oil filtered through a length of the second oil filter element is mixed with the oil filtered by the first oil filter element.
The fluid communication path preferably includes an orifice providing passage for filtered oil into the open inner volume of the first oil filter element, where the orifice has an area that is significantly smaller than an area of the second oil inlet. For example, the ratio of the area of the second oil inlet to the area of the orifice is about 1:400 or greater (e.g., in a range of about 1:400 to about 1:2000, proportional to the size and capacity of the filter.).
In a preferred embodiment the fluid communication path further includes a third oil filter element disposed between the top surface of the second oil filter element and the orifice, wherein the third oil filter element also filters particles of a smaller size than the first oil filter element. The third oil filter element is disposed above the first oil filter element in a stacked arrangement, and the second oil filter element is disposed circumferentially about the length of the first oil filter element and the length of the third oil filter element.
In the presently preferred embodiment the pressure of the oil at the second inlet is x psi, the pressure of the oil at the outlet of the filter housing is about x psi minus about 2% to about 6%, and the pressure of the oil at the orifice is about x psi minus about 0.2% to about 0.8%.
Preferably the housing is form and fit compatible with a conventional spin-on oil filter.
The teachings of this invention thus provide a hybrid oil filter assembly that is form and fit compatible with a conventional spin-on oil filter assembly. The hybrid oil filter assembly includes a housing and contained within the housing is a first oil flow path containing a first oil filter element for filtering particles having a first minimum size, as well as a second oil flow path containing a second oil filter element that surrounds the first oil filter element along the length thereof. The second oil filter element filters particles having a second minimum particle size that is smaller than the first minimum particle size. Oil in the first oil flow path that has been filtered by the first oil filter element and oil in the second oil flow path that has been filtered (micro-filtered) by the second oil filter element are mixed together within a void contained within the first oil filter element before being discharged from the hybrid oil filter assembly.
In the hybrid oil filter the pressure of the oil at an inlet of both of the first and second oil flow paths is x psi, the pressure of the oil at an outlet of the first oil flow path is x psi minus about 2% to about 6%, and the pressure of the oil at an outlet of the second oil flow path is x psi minus about 0.2% to about 0.8%.
The teachings of this invention also provide a method for filtering engine oil during the operation of an internal combustion engine. The method includes steps of (a) pumping engine oil into an inlet of an oil filter assembly; (b) filtering a first portion of the engine oil by passing the engine oil through a first oil flow path containing a first oil filter element for retaining particles having a first minimum size; (c) micro-filtering a second portion of the engine oil by passing the engine oil through a second oil flow path containing a second oil filter element that surrounds the first oil filter element, the second oil filter element retaining particles having a second minimum particle size that is smaller than the first minimum particle size; (d) mixing together, within a mixing zone contained within the first oil filter element, the engine oil from the first oil flow path that has been filtered by the first oil filter element and the engine oil from the second oil flow path that has been micro-filtered by the second oil filter element; and (e) discharging the mixed filtered and micro-filtered engine oil from an outlet of the oil filter assembly into the engine.
During execution of the method the pressure of the engine oil at the inlet of oil filter assembly, and at an inlet of both of the first and second oil flow paths, is x psi, the pressure of the engine oil at the outlet of the oil filter assembly is x psi minus about 2% to about 6%, and the pressure of the engine oil at an outlet of the second oil flow path is x psi minus about 0.2% to about 0.8%.